US6029527A - Fluid flow rate measuring and controlling device and method - Google Patents

Fluid flow rate measuring and controlling device and method Download PDF

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Publication number
US6029527A
US6029527A US09/045,064 US4506498A US6029527A US 6029527 A US6029527 A US 6029527A US 4506498 A US4506498 A US 4506498A US 6029527 A US6029527 A US 6029527A
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Prior art keywords
digital
value
analog
measuring
flow
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US09/045,064
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Kurt Seitz
Horst Adams
Markus Hasler
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Wagner International AG
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Wagner International AG
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Assigned to WAGNER INTERNATIONAL AG reassignment WAGNER INTERNATIONAL AG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ADAMS, HORST, HASLER, MARKUS, SEITZ, KURT
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
    • G01F1/50—Correcting or compensating means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
    • G01F1/36—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction
    • G01F1/363—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction with electrical or electro-mechanical indication
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L13/00—Devices or apparatus for measuring differences of two or more fluid pressure values
    • G01L13/06—Devices or apparatus for measuring differences of two or more fluid pressure values using electric or magnetic pressure-sensitive elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7758—Pilot or servo controlled
    • Y10T137/7759—Responsive to change in rate of fluid flow
    • Y10T137/776—Control by pressures across flow line valve

Definitions

  • the invention relates to control and measurement of the flow rate of a fluid.
  • Analog flow rate measuring and controlling units are known with which differential pressure measurement is effected by way of an orifice in a flow channel to determine the rate of flow. Following that, the value obtained by this measurement is compared with a desired value in a calculating unit. If the actual value differs from the desired value specified the calculating unit emits a correcting signal for application to a proportional valve unit which then initiates a correcting process to cause the measured value of the flow rate to coincide with the desired value.
  • a problem with the known flow rate measuring and controlling means is that they are relatively inflexible and cannot readily be matched to changes occuring in system components. Processing of the measurement and control data is substantially predetermined by the system components. While the digital components in their signal processing, fundamentally, are quite free of variations of operating parameters which may occur in the course of operation (e.g. due to aging of the components, thermal drifts, etc.), the sensors, analog amplifiers, analog comparators, and the like are influenced by such drifts.
  • an object of the instant invention to provide a device and a method by which to measure and control the flow rate of a fluid with improved reliability and less susceptibility to disturbance of the measuring and control system while, at the same time, offering maximum flexibility for influencing measurement and control data.
  • a fluid flow rate measuring and controlling method and device which are characterized variously in that the digital values are corrected by an offset value which depends on a change of the operating parameters of analog components of the measuring system in the course of operation of the measuring system, and in that values obtained from flow rate measurements are preprocessed and applied to a digital signal processor, and by correcting each digital value by an offset value which depends on a change of the operating parameters of analog components of the measuring device occurring in the course of operation of the measuring device, and by digitally preprocessing the values obtained, and by a digital signal processor for central control of the flow rate.
  • the instant invention thus provides methods and devices by means of which signals of the flow rate measurement are largely processed digitally and applied to a digital signal processor (DSP).
  • DSP digital signal processor
  • the signals supplied by the flow rate measuring means first are subjected to digital preprocessing so that any measurement uncertainties due to changes in the analog measuring components, such as thermal drift, are widely compensated.
  • the digital signal processor controls a digital control unit, preferably with the assistance of data from specific digital memory units, and the digital control unit in turn controls a valve unit by way of a valve regulator.
  • the control unit includes a PID controller.
  • a controller with any desired combination of P-, D-, and I-proportions may also be used, depending on the particular application.
  • the valve regulating means preferably comprises a pulse width modulator, and the valve means preferably includes a proportional valve.
  • the signal processing which largely is digital allows maximum flexibility and reliability of the measuring and control system.
  • the analog measured values obtained are converted into digital values which can be corrected, in the digital sphere, by an offset value in order to compensate a change of analog operating parameters of the measuring system occurring in the course of operation, in particular thermal drifting and the like.
  • the simplest way of determining the offset value is by obtaining an analog measured value during interruptions of the operation, when the volumetric flow is zero, and converting it into a digital value. Theoretically, this digital value also would have to be zero when there is zero flow. However, because of the variation or drift mentioned of the analog components, this digital value normally is not equal to zero, and it may be stored directly in an offset memory as the corrective value to be used when the operation of the system is resumed.
  • variable operating parameters especially tables or families of curves
  • special parameters, characteristics, and the like for control or regulation of the valve unit may also be provided for disturbances or abnormal operating conditions and interruptions of operation, as will be explained in greater detail below.
  • FIG. 1 shows a preferred embodiment of the flow rate measuring device according to the instant invention
  • FIG. 2 shows a preferred embodiment of a the flow rate control device according to the instant invention, cooperating with the flow rate measuring device.
  • FIG. 1 is a schematic block diagram of the flow rate measuring device, or p unit, according to the invention.
  • a flow channel 1 may be seen in which there is a restrictor or orifice 2.
  • a gaseous or liquid medium (fluid) flows in the flow channel in the direction indicated by arrow 3.
  • a first pressure sensor 4 is provided in the wall of the flow channel 1 to measure the pressure P 1 in the flow channel upstream of the orifice 2.
  • a second pressure sensor 5 is located downstream of the orifice 2 to measure the pressure P 2 in the flow channel 1 directly behind the orifice 2.
  • the pressure gauges or pressure sensors 4 and 5 convert the pressure values obtained into analog electrical signals which are applied to a differential amplifier 6.
  • the pressure difference p is a measure of the volumetric flow of the medium passing through the flow channel.
  • the signal output of the differential amplifier 6 is applied to an analog amplifier 7 which amplifies the signal amplitude in such a range that it will be the optimum for a subsequent analog/digital converter (ADC) 8.
  • ADC analog/digital converter
  • the analog/digital converter 8 converts the differential pressure signal which so far was analog into a digital value.
  • the analog components of the measuring system in particular sensors 4 and 5 as well as the amplifiers 6 and 7, suffer from an alteration of their operating parameters in the course of operation of the measuring system. They are influenced by thermal drifting, aging, maladjustments, and displacements, etc.
  • the instant invention provides an offset memory 9 to compensate this change in operating parameters of the analog components.
  • the offset memory 9 stores the value furnished by the analog/digital converter. To this end, at least one analog measured value is recorded during such operational interruptions. Ideally, this digital value should be zero when the fluid flow is zero. However, because of the drifts mentioned of the analog components, this value, as a rule, does not equal zero and it may be drawn upon in practice as a correcting value. The digital value of zero volumetric flow is stored in the offset memory 9.
  • the offset value stored in the offset memory 9 is inverted and read.
  • the offset value with its inverted sign is input into an adder 10 where it is added to the value supplied by the analog/digital converter.
  • the offset value which depends on the drift is subtracted from the digital value which corresponds to the measured value so that, essentially, only the pure measured signal is processed further.
  • Flow operations may be interrupted at any time in order to accomplish the balancing, i.e. to record the offset value which is dependent on the drift. Balancing either is effected during a natural interruption of operations, or such interruption may be provoked by active control at certain intervals in time.
  • the flow is interrupted with the aid of a proportional valve unit which will be described in greater detail below.
  • the (corrected) signal from the analog/digital converter 8 is input into a linearizer 11 which is followed by a standardizer 12 so that upon linearization in the linearizer 11 and standardization in the standardizer 12, e.g. to an input pressure P 1 measured at the pressure sensor 4, a signal reflecting the volumetric flow of the fluid in the flow channel 1 in standard meters 3 /hour (Nm 3 /h) will be available at the output of the measuring device.
  • the measuring device further may comprise a scaling or gauging memory 13 which stores gauging parameters to enable the measured value output by the standardizer 12 to be gauged again to the actual volumetric flow after the orifice 2 has been exchanged. That is especially advantageous if manufacturing tolerances of the orifice dimension are to be balanced.
  • the measuring device is gauged with respect to an external gauging means and the correcting values required are stored digitally in the gauging memory 13.
  • the correcting values which are recorded in the gauging memory 13 are impressed on the digital measured signal by means of a multiplier 14.
  • the measuring device is highly advantageous over the known state of the art in that the largely digital signal processing with the assistance of the offset memory 9 helps to compensate changing operational parameters of the analog components occurring in the course of time during service of the measuring device. These changes above all relate to thermal drifts, aging of the components, and the like. Moreover, it is easy to incorporate in the measuring system additional gauging to various orifice diameters, flow channel diameters, pressure gauge characteristics, or other hardware parameters specific of a particular installation, as well as fluid properties. Adequate sets of parameters and correcting values are simply stored in the gauging memory 13. It is likewise possible to provide for subsequent external loading of the gauging memory with values for correction.
  • FIG. 2 is a basic diagram of a digital flow-through device for gases and liquids, which device preferably operates in combination with the flow rate measuring device of FIG. 1.
  • This device receives the actual flow rate values from the flow rate measuring device in digital form and preferably preprocessed, as described above.
  • the flow rate control device illustrated in FIG. 2 further processes these signals in digital form so as to drive a proportional valve unit 15 which controls the volumetric flow of the gaseous or liquid medium (fluid) in the flow channel 1.
  • the basic elements of the flow rate control device are a digital controller 17 and a regulating means 18.
  • the controller 17 preferably is a PID controller, but a proportional controller may also be implemented by proper selection of the P-, I-, and D-proportions, and a PI controller may be used as well.
  • the regulating means 18 preferably includes a pulse width modulator which feeds control signals to the proportional valve unit 15.
  • the proportional valve of course, may be replaced by any other suitable valve means.
  • the digital flow rate control there is at least one additional memory means for storing variable operating parameters. It stores regulating parameters for the pulse width modulator 18 and/or control parameters for the controller 17.
  • This memory means preferably is adapted to be programmed. It is also possible to provide for external input of operating parameters into this memory.
  • the digital signal processor 16 preferably is linked to an external network.
  • the memory means comprises a control parameter memory 19 and a regulating parameter memory 20.
  • the control parameter memory 19 is a PID setting memory and the regulating parameter memory 20 is a PWM setting memory.
  • FIG. 2 demonstrates how the various elements are interconnected.
  • Flow rate control takes place as follows:
  • the digital actual flow rate value from the flow rate measuring device of FIG. 1, duly corrected, linearized, and standardized, if desired, is input into the digital signal processor (DSP) 16.
  • a desired flow rate value may be entered into a second input terminal of the DSP 16.
  • the DSP 16 compares the actual and desired values and generates a digital output signal which reflects the difference between those two values. This output signal is applied to the controller 17 connected downstream.
  • the controller 17 generates a corresponding control signal for the pulse width modulator (PWM) 18 which is connected downstream thereof and in turn drives the proportional valve unit 15.
  • PWM pulse width modulator
  • the proportional, integral, and differential portions of the control characteristic of the controller 17 needed for the control operation either may be given directly by the DSP 16 or fetched from the additional PID setting memory 19.
  • the latter is useful particularly if the control characteristic of the flow rate control device is to be matched to a specific plant configuration.
  • the control parameters preferably are optimized once prior to putting the plant into operation and then are firmly stored digitally in the PID setting memory 19. This way of proceeding is referred to as the static method.
  • the optimum proportional, integral, and differential portions destined for the controller 17 are each determined in response to the respective operating condition.
  • the DSP 16 determines an operating state based on an operating state signal which is entered into the DSP 16 from any part of the plant or from an external network.
  • the DSP 16 either may calculate the proportional, integral, and differential proportions itself, i.e. the parameters for the controller 17, or it may take access to corresponding values in the PID setting memory 19 in order to properly adjust the controller 17.
  • the PID setting memory it is convenient for the PID setting memory to contain a plurality of sets of parameters, or families of curves for the operating states, etc.
  • the static and dynamic methods also may be used in combination.
  • the predetermined parameters to be given the controller 17 are taken from the PID setting memory 19, and during special operating states (e.g. start-up of the plant, extreme deviation of the actual value from the desired value, or disturbances of the plant) the DSP 16 takes over the fixing of the control characteristic as soon as it has been informed of this extraordinary state of affairs.
  • a PWM 18 is provided to drive the proportional valve unit 15.
  • the proportional valve unit 15 In the embodiment shown in FIG. 2 it is associated with a pulse width modulator setting memory 20.
  • This memory stores certain drive functions of the PWM 18 to which direct access may be had, in response to the operating states determined in the DSP 16, in order to drive the PWM 18, i.e. the regulating means, directly in respect of these operating states.
  • Provision of the PWM setting memory 20 makes it unnecessary to take the detour via calculating or predetermining the PID parameters for the controller 17 and their application in the controller. This may be particularly useful, for example, if the flow-through must be stopped completely for a short time (e.g. to determine the drift correction values for the offset memory of FIG. 1) and, immediately afterwards, the control values valid before the shut-down are to be returned to.
  • the big difference between the actual and desired values upon renewed switch-on in this case would first cause the differential part of the PID controller 17 to be activated, then the proportional part, and finally the integral part and that would involve a considerable delay in time before the proportional valve unit 15 reached the given desired value once more.
  • the DSP 16 with the assistance of the PWM setting memory 20, can fetch the adequate setting value for the desired operating state immediately and feed it directly into the PWM 18. In this manner the desired operating state is reached very quickly.
  • PWM setting memory 20 serves for memorizing and quick recalling of PID controller parameters for the controller 17, especially so as to adapt the control characteristic of the flow rate control device to certain plant configurations.
  • PWM setting memory serves for memorizing and quick recalling of pulse width modulation parameters, especially so as to permit rapid, purposive control of the proportional valve unit 15 in case of special operating conditions or disturbances of the plant. Provision may be made for this control via the PWM setting memory to have precedence over the input of the correcting variables from the controller 17.
  • Certain operating states as well as sets of parameters for both memories 18 and 19 also may be input via a higher-level network.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Flow Control (AREA)
  • Measuring Volume Flow (AREA)
US09/045,064 1997-04-02 1998-03-19 Fluid flow rate measuring and controlling device and method Expired - Lifetime US6029527A (en)

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DE1997113668 DE19713668A1 (de) 1997-04-02 1997-04-02 Vorrichtung und Verfahren zum Messen und zum Regeln des Durchflusses eines Fluids
DE19713668 1997-04-02

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US (1) US6029527A (zh)
EP (1) EP0869335A3 (zh)
JP (1) JPH10325743A (zh)
KR (1) KR19980080866A (zh)
CN (1) CN1202616A (zh)
BR (1) BR9806396A (zh)
DE (1) DE19713668A1 (zh)
TW (1) TW414863B (zh)

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US6220747B1 (en) * 1997-08-14 2001-04-24 Michael Gosselin Proportional pump system for viscous fluids
WO2002027277A1 (en) * 2000-09-27 2002-04-04 Blease Medical Equipment Limited Apparatus and method for measuring fluid flow
US6591695B1 (en) * 1996-05-07 2003-07-15 Efg & E International Flow metering device for landfill gas extraction well
US6609431B1 (en) 2000-09-29 2003-08-26 Xellogy, Inc. Flow measuring device based on predetermine class of liquid
US6619138B2 (en) * 1999-07-07 2003-09-16 Westinghouse Air Brake Technologies Corporation Apparatus for dynamically adjusting size of an orifice to increase accuracy in measuring the rate of air flow
US6645874B1 (en) * 1999-08-31 2003-11-11 Micron Technology, Inc. Delivery of dissolved ozone
US6856251B1 (en) 2001-04-26 2005-02-15 Xsilogy, Inc. Systems and methods for sensing pressure
US20050229859A1 (en) * 2004-04-14 2005-10-20 Harvey Wayne A Controlled dilution system for drinking water and unit therefor
US6992590B1 (en) 2001-04-27 2006-01-31 Xsilogy, Inc. Systems and methods for sensing a fluid supply status
US20090292484A1 (en) * 2008-05-23 2009-11-26 Wiklund David E Multivariable process fluid flow device with energy flow calculation
US20120101638A1 (en) * 2010-10-22 2012-04-26 Chan Li Machinery Co., Ltd. Optimum proportional-integral-derivative (pid) control method for adapting a process facility system
US20130167811A1 (en) * 2011-12-30 2013-07-04 Caterpillar Inc. Egr flow sensor for an engine
US20130240045A1 (en) * 2012-03-15 2013-09-19 Xiufeng Pang Method for Determining a Fluid Flow Rate With a Fluid Control Valve
US8754720B2 (en) 2011-08-03 2014-06-17 Mi Yan Two-stage pulse signal controller
US10466127B2 (en) * 2010-11-03 2019-11-05 Avgi Engineering, Inc. Differential pressure transmitter with intrinsic verification
US10520954B2 (en) * 2015-05-29 2019-12-31 Norgren Limited Active cancellation of a pulsating flow with a flow signal noise reference

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DE19753660C2 (de) * 1997-12-03 2001-01-25 Wagner Internat Ag Altstaetten Verfahren und Einrichtung zum Aufbringen eines Trennmittels auf eine Spritzgußform
DE19808765A1 (de) * 1998-03-02 1999-09-16 Wagner Int Pulverbeschichtungsanlage und -verfahren zum Speisen und Mischen von Pulver in einer Beschichtungsanlage
DE19811341A1 (de) * 1998-03-16 1999-09-30 Wagner Int Verfahren und Einrichtung zum Bestimmen der Zusammensetzung von fluidisierbaren Feststoffpartikeln
DE19853262A1 (de) * 1998-11-18 2000-05-25 Bsh Bosch Siemens Hausgeraete Regelung der Brennerheizleistung bei einem gasbetriebenen Koch- oder Backgerät
DE10111383B4 (de) * 2001-03-09 2006-02-09 Wagner International Ag Verfahren zur Förderung von Beschichtungspulver zu einer Beschichtungseinheit und zugehörige Pulverfördervorrichtung
JP5069839B2 (ja) * 2001-10-12 2012-11-07 ホリバ エステック，インコーポレーテッド 質量流量装置を作製および使用するためのシステム及び方法
DE10210436A1 (de) * 2002-03-09 2003-10-02 Michael Licht Verfahren und Vorrichtung zur zerstörungsfreien spektroskopischen Bestimmung von Analytkonzentrationen
DE102006018219A1 (de) * 2006-04-19 2007-10-25 Festo Ag & Co Mit einem Regler versehenes Stetigventil, insbesondere Proportionalventil
JP5499381B2 (ja) * 2009-10-20 2014-05-21 日立金属株式会社 流量制御装置
WO2014083340A1 (en) * 2012-11-30 2014-06-05 Imperial Innovations Limited A device, method and system for monitoring a network of fluid-carrying conduits

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6591695B1 (en) * 1996-05-07 2003-07-15 Efg & E International Flow metering device for landfill gas extraction well
US6220747B1 (en) * 1997-08-14 2001-04-24 Michael Gosselin Proportional pump system for viscous fluids
US6619138B2 (en) * 1999-07-07 2003-09-16 Westinghouse Air Brake Technologies Corporation Apparatus for dynamically adjusting size of an orifice to increase accuracy in measuring the rate of air flow
US6645874B1 (en) * 1999-08-31 2003-11-11 Micron Technology, Inc. Delivery of dissolved ozone
US20040194883A1 (en) * 1999-08-31 2004-10-07 Torek Kevin J Delivery of dissolved ozone
US20040211514A1 (en) * 1999-08-31 2004-10-28 Torek Kevin J. Delivery of dissolved ozone
WO2002027277A1 (en) * 2000-09-27 2002-04-04 Blease Medical Equipment Limited Apparatus and method for measuring fluid flow
US6609431B1 (en) 2000-09-29 2003-08-26 Xellogy, Inc. Flow measuring device based on predetermine class of liquid
US6856251B1 (en) 2001-04-26 2005-02-15 Xsilogy, Inc. Systems and methods for sensing pressure
US6992590B1 (en) 2001-04-27 2006-01-31 Xsilogy, Inc. Systems and methods for sensing a fluid supply status
US20050229859A1 (en) * 2004-04-14 2005-10-20 Harvey Wayne A Controlled dilution system for drinking water and unit therefor
US7201113B2 (en) * 2004-04-14 2007-04-10 Iosolutions Incorporated Controlled dilution system for drinking water and unit therefor
US8849589B2 (en) 2008-05-23 2014-09-30 Rosemount Inc. Multivariable process fluid flow device with energy flow calculation
WO2009143447A1 (en) * 2008-05-23 2009-11-26 Rosemount, Inc. Multivariable process fluid flow device with energy flow calculation
US20090292484A1 (en) * 2008-05-23 2009-11-26 Wiklund David E Multivariable process fluid flow device with energy flow calculation
US20120101638A1 (en) * 2010-10-22 2012-04-26 Chan Li Machinery Co., Ltd. Optimum proportional-integral-derivative (pid) control method for adapting a process facility system
CN102455659A (zh) * 2010-10-22 2012-05-16 全利机械股份有限公司 工艺设备系统的最佳化pid控制方法
US10466127B2 (en) * 2010-11-03 2019-11-05 Avgi Engineering, Inc. Differential pressure transmitter with intrinsic verification
US8754720B2 (en) 2011-08-03 2014-06-17 Mi Yan Two-stage pulse signal controller
US20130167811A1 (en) * 2011-12-30 2013-07-04 Caterpillar Inc. Egr flow sensor for an engine
US8938961B2 (en) * 2011-12-30 2015-01-27 Caterpillar Inc. EGR flow sensor for an engine
US20130240045A1 (en) * 2012-03-15 2013-09-19 Xiufeng Pang Method for Determining a Fluid Flow Rate With a Fluid Control Valve
US10520954B2 (en) * 2015-05-29 2019-12-31 Norgren Limited Active cancellation of a pulsating flow with a flow signal noise reference

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TW414863B (en) 2000-12-11
DE19713668A1 (de) 1998-10-08
KR19980080866A (ko) 1998-11-25
JPH10325743A (ja) 1998-12-08
EP0869335A3 (de) 1999-07-28
EP0869335A2 (de) 1998-10-07
BR9806396A (pt) 1999-11-23
CN1202616A (zh) 1998-12-23

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